Evidence for nonhadronic degrees of freedom in the transverse mass spectra of kaons from relativistic nucleus-nucleus collisions?

Abstract

We investigate transverse hadron spectra from relativistic nucleus-nucleus collisions which reflect important aspects of the dynamics - such as the generation of pressure - in the hot and dense zone formed in the early phase of the reaction. Our analysis is performed within two independent transport approaches (HSD and UrQMD) that are based on quark, diquark, string and hadronic degrees of freedom. Both transport models show their reliability for elementary $pp$ as well as light-ion (C+C, Si+Si) reactions. However, for central Au+Au (Pb+Pb) collisions at bombarding energies above $\sim$ 5 A$\cdot$GeV the measured $K^{\pm }$ transverse mass spectra have a larger inverse slope parameter than expected from the calculation. Thus the pressure generated by hadronic interactions in the transport models above $\sim$ 5 A$\cdot$GeV is lower than observed in the experimental data. This finding shows that the additional pressure - as expected from lattice QCD calculations at finite quark chemical potential and temperature - is generated by strong partonic interactions in the early phase of central Au+Au (Pb+Pb) collisions.

4 pages, 3 figures,discussions extended, references added, to be published in Phys. Rev. Lett

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• Chiral symmetry restoration versus deconfinement in heavy-ion collisions at high baryon density
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• Kaon and Pion production in relativistic heavy-ion collisions
• Fluctuations of the $K/\pi$ Ratio in Nucleus-Nucleus Collisions: Statistical and Transport Models
• Energy dependence of transverse mass spectra of kaons produced in p+p and p+pbar interactions.A compilation
• Extraction of the sound velocity from rapidity spectra: Evidence for QGP formation at FAIR/RHIC-BES energies
• Multiplicity Fluctuations in Nucleus-Nucleus Collisions: Dependence on Energy and Atomic Number
• Strangeness dynamics in relativistic nucleus-nucleus collision
• Transverse Pressure and Strangeness Dynamics in Relativistic Heavy Ion Reactions
• Pion freeze-out as seen through HBT correlations in heavy ion collisions from FAIR/AGS to RHIC energies
• Transport model analysis of the transverse momentum and rapidity dependence of pion interferometry at SPS energies
• Dynamics of strange, charm and high momentum hadrons in relativistic nucleus-nucleus collisions
• Transverse-Mass Spectra in Heavy-Ion Collisions at energies E_{lab} = 2--160 GeV/nucleon
• What is so special about strangeness in hot matter?
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• Expansion dynamics of Pb-Pb collisions at 40 A GeV/c viewed by negatively charged hadrons
• Transverse momentum spectra of hadrons produced in central heavy-ion collisions
• Properties of the partonic phase at RHIC within PHSD
• Excitation Function of the Longitudinal Expansion in Central Nuclear Collisions
• Probing the QGP Phase Boundary with Thermal Properties of $\varphi$ Mesons
• The QGP phase in relativistic heavy-ion collisions
• Parton-hadron matter in- and out-off equilibrium
• Parton-hadron dynamics in heavy-ion collisions
• Kaon production from 1 to 40 A GeV
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• The quest for the quark-gluon plasma from the perspective of dynamical models of relativistic heavy-ion collisions